Today, the most common modality for optical signal amplification is the rare-earth doped fiber amplifier. These devices have good amplification characteristics and a well-understood long-term behavior. Moreover, they can be added to a fiber link via fiber splicing, which is a low insertion loss coupling technique.
An alternative amplification modality is the semiconductor optical amplifier (SOA). SOA systems have a number of advantages relative to the common erbium-doped amplifier scheme. SOA""s are typically electrically, rather than optically, pumped. As a result, they can be more efficient and avoid the need for ancillary, expensive optical pump devices. Moreover, they are usually physically smaller than fiber amplifiers, which require a relatively long length of doped fiber. This last characteristic is especially relevant when amplification is required in larger systems offering higher levels of functionality.
For example, integrated switching and amplification capabilities are relevant to optical applications such as metro WDM. In such applications, the dynamic routing of individual wavelength slots or channels to form multichannel wavelength division multiplexed (WDM) optical signals is important functionality, especially if it can be provided in small, low-cost systems.
The present invention concerns an optical amplifier array that is integrated with a switching matrix. Further, in a preferred embodiment, a tunable filter is further integrated into the system. As a result, switching and amplification can be performed in a common hermetic package, for example, thus offering advantages associated with small footprint and low cost. The optional integration of the tunable filter, with or without the switching matrix, further allows for the monitoring of the separate optical links to ensure the proper routing of signals and/or proper spectral slotting of the various channels in each of the WDM optical signals.
In general, according to one aspect, the invention features a multi-channel semiconductor optical amplifier system. The system comprises an optical bench. A first array and second array of fibers, having endfaces, are secured relative to the optical bench. A semiconductor optical amplifier array is installed optically between the endfaces of the first array and the endfaces of the second array to provide for optical amplification of optical signals being transmitted between the two arrays.
In the illustrated embodiment, the optical amplifier array is implemented as separate semiconductor chips. Alternatively, multi-striped chips can be utilized providing for further integration.
In the preferred embodiment, an isolator is installed on the optical bench between the endfaces of the first fiber array and the semiconductor optical amplifier array. Such isolators are useful to prevent the SOA""s from lasing on any back-reflected signals.
Typically, in the preferred embodiment, two isolator systems are used, one between the first array and the SOA""s and a second between the SOA""s and the second array. Collimating lenses are typically required and are installed on the optical benches to couple light, from the first fiber array, into the semiconductor optical amplifier array.
Preferably, to provide for WDM monitoring, a tunable filter is installed on the bench to provide for the spectral analysis or filtering of optical signals from the first array of fibers. A detector is used to then detect the filtered optical signal. Further, to allow the filter to sample any one of the beams from the first array of fibers, an array of filter optical switches is provided that selectively transmits optical signals from one of the fibers in the first array to the tunable filter.
In general, according to another aspect, the invention further features a multi-channel semiconductor switch system with optical amplification. This system comprises an optical bench and first, second, and third arrays of fibers, having endfaces that are secured relative to the optical bench. In one embodiment, the first array of fibers functions as an input port and the second and third arrays function as output ports.
In order to provide for the switching functionality, an array of optical switches is located between the first array of fibers and the second and third array of fibers. These switches allow beams emitted from the first array of fibers to be selectively coupled to either the second or third array of fibers.
The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.